1. Field of the Invention
This invention relates to computer systems and, more particularly, to apparatus for providing an interface connection between a device operating on signals provided in the MIDI standard and a device capable of of sending and receiving signals through a standard RS 232 interface.
2. History of the Prior Art
The computer industry is presently trying to provide systems which allow an operator to receive, utilize, and transmit information from many different sources. A primary one of these sources is sound systems. As the electronics industry has converted to systems which use digital signals for transferring and manipulating sound, it has developed a standard referred to as MIDI for handling those signals. In general, the MIDI standard provides that certain signals will be available at certain terminals of a defined five-pin plug connector. Most computer systems developed to date are not equipped with MIDI terminals so input is handled through a RS 232 serial terminal with which most desktop computers are equipped.
Unfortunately, although RS 232 terminals are designed to a standard, all RS 232 terminals are not the same. For example, some RS 232 terminals transfer and receive signals which vary by a maximum of fifteen volts from a standard ground voltage while others transfer and receive signals which vary by a minimum of only three volts. Some computers provide the voltage variation from a base of ground while other computers provide the voltage variation from some other base. Some computers have provision for automatically sensing input signals and refuse to operate when a voltage level appears at particular pins upon start up.
For all of these reasons, MIDI to RS 232 interfaces are not what would normally be termed standard throughout the industry and have heretofore been provided on an ad hoc basis.